I find VGA cable over HDMI if your TV supports VGA in and your Vid card can match the native resolution of the TV. I run VGA to my TV at 1366X768, (the actual native resolution of the TV) no resizing needed, if I use HDMI then the TV would have to resize the pic to 720P. Slightly better pic using VGA, nothing you would notice watching a movie but definitely sharpens up the text when using it as a 2nd monitor.
Edit: I just reread your question, at 1080P either should output to the native resolution 1920X1080 and in that case I would most likely choose HDMI. Digital over analog!